Generation of new harmonics caused by the processing of DQ transformation in power quality compensators

An event appearing when executing the DQ transformation to get the compensation references in power quality compensators is presented in this work, where new harmonics that had not existed initially are generated and inserted to the electric system. Although the new harmonics have low magnitude, they exist, and correct processing of control techniques should be guaranteed to avoid amplifying their magnitudes. The new harmonics are produced by the filtering act in the dq frame, since filter is not ideal. The appearance of the new harmonics occurs only if the d component is filtered to isolate the dc term in the dq reference frame. But, if both d and q signals are filtered, no new harmonics are generated. This phenomenon is studied for general unbalanced systems; detailed analyses, proofs, simulation, and experimental tests are presented to validate the existence of the generation of new harmonics.